A rotary kiln foundation pile foundation diagnosis and reinforcement method and reinforcement system

Abstract

This invention discloses a diagnostic and reinforcement method and system for rotary kiln foundation pile foundations, relating to the field of rotary kiln testing technology. The method includes: acquiring vibration data; determining whether the vibration originates from structural damage to the foundation based on the correlation between the vibration data and the rotary kiln's rotation frequency; if so, scanning all engineering piles to determine the defect type, location, and loss depth range of each pile; determining the critical depth at which each pile can still provide effective embedment under its current state based on the defect information, and assessing the overall remaining horizontal bearing capacity and flexural bearing capacity; and reinforcing based on the assessment results. The reinforcement system includes an integral composite pile cap consisting of an existing pile cap and a newly constructed, deepened pile cap, as well as multiple newly added pile foundations installed on the newly constructed, deepened pile cap. This invention solves the technical problems of poor reinforcement effects and the tendency to fall into a vicious cycle of "repeated damage and repeated reinforcement" in existing technologies through precise diagnosis, quantitative assessment, and optimized reinforcement, achieving permanent and reliable foundation reinforcement.

Description

Technical Field

[0001] This invention relates to the field of rotary kiln testing technology, and in particular to a method and system for diagnosing and reinforcing rotary kiln foundation piles. Background Technology

[0002] Rotary kilns are core thermal equipment in industries such as cement, metallurgy, and chemicals. Their massive, heavily loaded, tilted installations and low-speed rotation cause their supporting foundations (usually called kiln piers) to bear complex alternating loads from the equipment's own weight, torque, and vertical displacement. To ensure the stability and safety of the foundation, most kiln piers use pile foundations, with the area between the pile top and the pile cap being the most stress-concentrated part.

[0003] During long-term operation, the embedded area at the top of the pile is highly susceptible to damage due to fatigue accumulation or sudden external disturbances (such as earthquakes or vibrations from nearby construction). This damage typically manifests as crushing of the concrete at the pile top and shearing of the reinforcing steel, leading to a reduction in the effective embedment depth of the pile foundation and a significant decrease in its horizontal and flexural bearing capacity. When the damage accumulates to a certain extent, it can trigger harmful vibrations in the kiln pier and even the entire rotary kiln system. These vibrations often have enormous amplitudes (up to tens of millimeters), which not only seriously threaten the safe operation of the equipment itself but also cause large-scale detachment of refractory materials inside the kiln, resulting in huge economic losses and serious safety hazards.

[0004] To address the above problems, existing technologies typically employ two approaches: one is to rely on experience for diagnosis, which involves inferring the cause by observing vibration symptoms, lacking precise quantitative analysis and easily leading to misjudgment; the other is to use a "patchwork" reinforcement method during the reinforcement stage, which often involves simply adding a few piles around the original foundation or mechanically expanding the projected area of ​​the foundation.

[0005] However, in the process of implementing the technical solution of this application, the inventors discovered that the above-mentioned traditional method has the following defects: 1. Vague diagnostic process: Relying solely on experience to determine the source of vibration makes it impossible to accurately distinguish whether it is a mechanical failure of the equipment itself or damage to the foundation structure, resulting in a lack of targeted reinforcement measures.

[0006] 2. Blind Reinforcement Design: Reinforcement is carried out without determining the specific location, extent, and remaining bearing capacity of the pile foundation damage, resulting in highly unpredictable design. Newly added piles and pile caps often perpetuate the original unfavorable stress distribution, failing to scientifically reconstruct and optimize the load transfer path.

[0007] 3. Unoptimized stress mechanism: Simply adding piles or expanding the pile cap not only fails to enable the new structure to effectively resist the core moment and alternating load generated by the operation of the rotary kiln, but may even exacerbate stress concentration in key parts of the original structure by changing the local structural stiffness.

[0008] 4. Difficulty in achieving lasting results: The above-mentioned defects together cause the reinforcement measures to often fail in the short term, causing the project to fall into a vicious cycle of "repeated damage and reinforcement, repeated reinforcement and repeated damage", which not only brings continuous economic losses, but also creates long-term safety hazards.

[0009] Therefore, how to provide a technical solution that can accurately diagnose the root cause of damage, scientifically assess the remaining load-bearing capacity, and effectively reinforce the structure is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] This invention provides a method and system for diagnosing and reinforcing rotary kiln foundation pile foundations, in order to solve the following technical problems existing in rotary kiln foundation pile foundations in related technologies: The diagnostic methods are vague: existing technologies rely heavily on experience to determine the source of vibration, which cannot accurately distinguish between mechanical failures of equipment and damage to the foundation structure, easily leading to misjudgments and making subsequent reinforcement lack specificity; Blind reinforcement design: Reinforcement is carried out without identifying the specific location, extent and remaining bearing capacity of pile foundation damage. The design is highly blind and cannot "prescribe the right medicine", resulting in waste of resources and poor results. Unoptimized stress mechanism: Traditional reinforcement methods often follow the original unfavorable stress layout. The newly added structure cannot effectively resist the core moment and alternating load generated by the operation of the rotary kiln, and may even aggravate the stress concentration in key parts of the original structure. The reinforcement effect is not lasting: The above defects cause the reinforcement measures to fail in the short term, causing the project to fall into a vicious cycle of "repeated damage and reinforcement, repeated reinforcement and damage", resulting in continuous economic losses and long-term safety hazards.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: First, this invention provides a method for diagnosing and reinforcing rotary kiln foundation pile foundations, comprising the following steps: Obtain vibration data of the rotary kiln, and determine whether the vibration of the rotary kiln originates from damage to the basic structure based on the correlation between the vibration data and the rotation frequency of the rotary kiln. If yes, scan all the engineering piles supporting the rotary kiln to determine the defect type, location, and depth of loss for each pile; if no, end the diagnosis. Based on the defect type, location, and loss depth range of each engineering pile, the critical depth at which each engineering pile can still provide effective embedment under the current state is determined, and the overall remaining horizontal bearing capacity and flexural bearing capacity of all engineering piles are evaluated based on the critical depth to obtain the evaluation results. The engineering piles were reinforced based on the assessment results.

[0012] Preferably, the specific method for determining whether the vibration of the rotary kiln originates from structural damage based on the correlation between vibration data and the rotation frequency of the rotary kiln includes: The collected vibration data is used to generate a vibration spectrum diagram. One or more frequency components with significantly prominent amplitudes are identified from the spectrum diagram as the dominant vibration frequency. Calculate the theoretical rotational frequency and its harmonics based on the actual operating speed of the rotary kiln; The vibration dominant frequency is compared with the rotational frequency and its harmonics. If the vibration dominant frequency and the rotational frequency or its harmonics are basically consistent, it is determined that the vibration is not related to the structural damage of the foundation. If the vibration dominant frequency is one or more fixed low-frequency peaks that are not related to the rotational frequency, and the frequency component remains stable when the equipment speed changes, accompanied by a huge displacement amplitude, it is determined that the vibration originates from the structural damage of the foundation.

[0013] Preferably, the specific method for scanning all the engineering piles supporting the rotary kiln includes: Ground-penetrating radar was used to conduct a grid-based general survey and scan of the soil area under the rotary kiln foundation to preliminarily delineate the abnormal areas of the pile body. Based on the preliminary scan results, test holes were drilled at the determined locations of the engineering piles. Ultrasonic cross-hole CT imaging technology was used to measure the propagation velocity, energy attenuation, and waveform characteristics of ultrasonic waves in the pile concrete. By collecting data from different depths and profiles, a three-dimensional image of the internal structure of the pile was reconstructed. By comprehensively comparing and analyzing the results of ground-penetrating radar scanning and ultrasonic cross-hole CT imaging data, each engineering pile is analyzed to accurately determine its defect type, its longitudinal and transverse location on the pile body, and the range of damage depth along the pile body.

[0014] Preferably, the specific method for determining the critical depth at which each engineering pile can still provide effective embedment under its current state, based on the defect type, location, and loss depth range of each engineering pile, includes: Based on the defect type, location, and loss depth range of each engineering pile, a finite element model including the interaction between the pile, soil, and pile cap is established. Through finite element model inversion analysis, the critical depth at which each engineering pile can still provide effective embedment under the current state was determined.

[0015] Preferably, the specific method for reinforcing the engineering piles based on the evaluation results includes: Based on the critical depth, determine the bottom depth of the newly constructed and deepened foundation; New pile foundations will be constructed on the outside of the existing pile cap, and the arrangement direction of all new pile foundations will be perpendicular to the central axis of the rotary kiln. Excavate the earth to the bottom depth to create space for the new and deepened foundation. Combine the existing foundation with the new and deepened foundation through a synergistic reinforcement structure to form an integral composite foundation.

[0016] More preferably, the formula for determining the bottom depth of the newly constructed and deepened foundation is: D ≥ H critical + Δ In the formula, D is the bottom depth, and H is... critical The critical depth is Δ, and the safety reserve thickness is Δ≥0.2m.

[0017] More preferably, the synergistic enhancement structure includes one or more of the following measures: High-strength chemical anchors are implanted as the main shear keys; A pre-laid grouting network is laid out for pressure injection of epoxy resin grout at the interface. Laying carbon fiber composite fabric or bolted steel plates on the interface surface provides additional shear and tensile strength.

[0018] Preferably, the vibration data includes vibration acceleration, frequency, and displacement amplitude, which are acquired by arranging vibration sensors on the rotary kiln bearing seat and kiln pier.

[0019] Secondly, the present invention also provides a rotary kiln foundation pile foundation reinforcement system, applied to the diagnosis and reinforcement method for rotary kiln foundation pile foundations as described in any one of the first aspects, comprising: Integral composite foundation, including existing foundations and newly built, deepened foundations; Multiple new pile foundations were installed on the newly built and deepened pile cap.

[0020] Preferably, the bottom depth D of the newly constructed and deepened foundation satisfies: D ≥ H critical + Δ, where H critical Δ represents the critical depth, and Δ represents the safety reserve thickness.

[0021] Preferably, the arrangement direction of the newly added pile foundations is perpendicular to the central axis of the rotary kiln.

[0022] Preferably, a synergistic reinforcement structure is provided at the interface between the existing foundation and the newly built deepened foundation. The synergistic reinforcement structure includes one or more of the following: chemical anchoring, grouting network, carbon fiber composite fabric, or bolted steel plate.

[0023] By adopting the above technical solution, the present invention can achieve the following beneficial effects: First, it enables accurate identification of the vibration source. By analyzing the correlation between vibration data and rotational frequency, the dominant vibration frequency is accurately compared with the theoretical rotational frequency and its harmonics of the equipment. This effectively distinguishes between mechanical vibration and vibration caused by structural damage to the foundation, avoiding misjudgment at the source and providing a reliable scientific basis for deciding whether to initiate detailed pile foundation testing.

[0024] Secondly, it enables precise quantitative diagnosis of pile foundation damage. A two-stage detection method combining ground-penetrating radar survey and ultrasonic cross-hole CT imaging for detailed inspection allows for three-dimensional visualization of the defect type, location, and damage depth range of each engineering pile, elevating qualitative judgment to quantitative analysis and providing accurate input parameters for subsequent bearing capacity assessment.

[0025] Third, it enabled the scientific assessment of remaining bearing capacity. By importing damage data obtained from non-destructive testing into a refined finite element model for inversion analysis, the effective embedment critical depth of each engineering pile was determined. The establishment of this key parameter enabled the reinforcement design to accurately locate the starting position where each engineering pile still has complete bearing capacity, providing a scientific basis for the subsequent design of the bottom depth of the integral composite pile cap, and completely avoiding the drawbacks of insufficient or excessive reinforcement.

[0026] Fourth, it achieves a fundamental optimization of the stress-bearing mechanism. By accurately determining the depth of the new pile cap based on the critical depth, it ensures that the intact sections of all pile foundations are re-embedded at a deeper depth; through the innovative design of arranging piles perpendicular to the kiln centerline, the newly added pile foundation group can most effectively resist the main torque generated by the rotary kiln, fundamentally improving the stress-bearing mechanism of the pile cap.

[0027] Fifth, it achieved synergistic operation between the old and new structures. Through multiple synergistic reinforcement measures such as chemical anchoring, pre-embedded grouting, carbon fiber cloth or bolted steel plates, the old and new pile caps were reliably combined into an integral composite pile cap, successfully integrating the original pile foundation, the newly added pile foundation and the old and new pile caps into a unified whole that synergistically bears the load, and completely solving the traditional reinforcement problem of combining old and new concrete.

[0028] Sixth, it achieves durable and reliable reinforcement effects. This invention forms a complete technical closed loop from accurate diagnosis to quantitative assessment to optimized reinforcement, fundamentally eliminating the source of vibration, avoiding the vicious cycle of "repeated damage and repeated reinforcement" in traditional methods, ensuring the permanence and reliability of reinforcement, and achieving a balance between safety and economy.

[0029] Seventh, it has good application value. This invention is not only applicable to cement rotary kilns, but can also be extended to foundation reinforcement projects for other heavy rotating equipment in industries such as metallurgy and chemical engineering, with significant economic and social benefits.

[0030] In summary, this invention effectively solves the technical problems of difficult diagnosis and poor reinforcement effect of rotary kiln foundation pile foundation damage through systematic diagnostic methods, scientific evaluation means and optimized reinforcement schemes, and realizes a fundamental transformation from "local passive repair" to "overall active reinforcement". Attached Figure Description

[0031] Figure 1 This is a flowchart of the diagnostic and reinforcement method for rotary kiln foundation piles disclosed in this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] The following is in conjunction with the appendix Figure 1 This application provides a detailed description of a diagnostic and reinforcement method and system for rotary kiln foundation piles through specific embodiments and application scenarios.

[0035] Example 1 This embodiment provides a method for diagnosing and reinforcing rotary kiln foundation pile foundations, including the following steps: Step 100: Obtain vibration data of the rotary kiln. Based on the correlation between the vibration data and the rotation frequency of the rotary kiln, determine whether the vibration of the rotary kiln originates from damage to the basic structure.

[0036] Specifically, in a cement plant production line, the No. 3 rotary kiln has experienced abnormal vibrations in recent years, with kiln block amplitudes reaching 8-12 mm, seriously affecting production safety. To investigate the cause of the vibration, vibration sensors were installed on the top of each bearing seat and corresponding kiln block of the rotary kiln. These vibration sensors are triaxial accelerometers (such as the PCB 356A16 type), capable of simultaneously acquiring vibration acceleration signals in the X, Y, and Z directions. The sampling frequency was set to 200Hz, and continuous data collection was conducted for 24 hours, covering operating data under different load conditions of the rotary kiln. The vibration data includes vibration acceleration, frequency, and displacement amplitude, where the displacement amplitude is obtained by double integration of the acceleration signal.

[0037] Step 110: Generate a vibration spectrum diagram from the collected vibration data, and identify one or more frequency components with significantly prominent amplitudes from the spectrum diagram as the dominant vibration frequency.

[0038] The acquired vibration time-domain signal was subjected to Fast Fourier Transform (FFT) to generate a vibration spectrum. Analysis of the spectrum revealed significant amplitude peaks at 1.2 Hz, 2.4 Hz, and 4.8 Hz, with the amplitude at 1.2 Hz being the most prominent, reaching 0.8 mm / s.

[0039] Step 120: Calculate the theoretical rotational frequency and its harmonics based on the actual operating speed of the rotary kiln.

[0040] Checking the operating parameters of the rotary kiln, its current rotational speed is 3.2 r / min, so its fundamental frequency is 3.2 / 60 ≈ 0.053 Hz, its second harmonic is 0.106 Hz, and its fourth harmonic is 0.212 Hz. However, the measured dominant vibration frequency of 1.2 Hz is much higher than the harmonics of the rotational frequency.

[0041] Step 130: Compare the dominant vibration frequency with the rotational frequency and its harmonics.

[0042] A comparison of the 1.2Hz dominant frequency with 0.053Hz and its harmonics revealed a complete mismatch. Furthermore, it was found that during the adjustment of the rotary kiln speed (from 3.0 r / min to 3.4 r / min), the 1.2Hz frequency component remained stable, and the displacement amplitude of the kiln pier consistently remained above 8 mm. According to vibration analysis theory, if the dominant vibration frequency is independent of the rotational speed and exhibits a fixed low-frequency peak, accompanied by a large displacement amplitude, then the vibration can be determined to originate from structural damage to the foundation, rather than a mechanical failure of the equipment itself. Therefore, the preliminary diagnostic conclusion is that the abnormal vibration of the rotary kiln originates from structural damage to the foundation piles.

[0043] Step 200: If yes, scan all the engineering piles supporting the rotary kiln to determine the defect type, location, and depth of loss for each pile; if no, end the diagnosis.

[0044] Since step 100 determined that the vibration originated from foundation damage, a detailed pile foundation inspection procedure was initiated.

[0045] Step 210: Use ground-penetrating radar and ultrasonic cross-hole CT imaging technology to scan all the engineering piles supporting the rotary kiln, and determine the defect type, location and damage depth range of each pile in three-dimensional visualization.

[0046] First, a grid-based survey of the soil beneath the kiln pier foundation was conducted using ground-penetrating radar (such as the Italian IDS RIS series). A combination of 200MHz and 400MHz antenna frequencies was selected for the ground-penetrating radar, with a survey line spacing of 0.5m. By analyzing the waveform, amplitude, and arrival time of the radar reflected waves, the locations of eight engineering piles were identified. Preliminary findings indicated that six of these piles exhibited significant abnormal reflection signals within a range of 0.5m-2.0m below the pile top, characterized by features such as phase axis misalignment and enhanced reflected wave amplitude, preliminarily identifying these as areas of pile defects.

[0047] Based on the preliminary results of ground-penetrating radar, 2-3 parallel ultrasonic testing holes were drilled around each of the six suspected defective piles. The holes were 50mm in diameter and more than 2m deeper than the estimated defect depth. An ultrasonic cross-hole CT imaging system (such as the Russian IDSA in-hole ultrasonic testing system) was used. The ultrasonic transmitting and receiving probes were placed in two different boreholes of the same pile, and were synchronously raised from the bottom of the borehole at a step distance of 0.1m. The propagation velocity, energy attenuation, and waveform characteristics of the ultrasonic waves in the pile concrete were collected point by point. A three-dimensional image of the internal structure of the pile was reconstructed using a tomographic inversion algorithm.

[0048] By comprehensively comparing and analyzing the results of ground-penetrating radar scanning and ultrasonic cross-hole CT imaging, the following detection results were obtained for each engineering pile: Pile #1: A circumferential crack exists in the range of 0.8m-1.5m below the pile top. The defect type is crack, and the loss depth ranges from 0.7m. #2 pile: Concrete segregation occurs in the range of 0.5m-1.2m below the pile top. The defect type is segregation, and the loss depth range is 0.7m. Pile #3: There is a broken pile in the range of 1.0m-2.2m below the top of the pile. The defect type is fracture, and the loss depth range is 1.2m. The remaining 5 piles were found to have no obvious defects or defects less than 0.3m in depth, and were considered to be basically intact.

[0049] Step 300: Based on the defect type, location, and loss depth range of each engineering pile, determine the critical depth at which each engineering pile can still provide effective embedment under the current state, and evaluate the overall remaining horizontal bearing capacity and flexural bearing capacity of all engineering piles based on the critical depth to obtain the evaluation results.

[0050] Step 310: Establish a finite element model based on the defect type, location, and loss depth range of each engineering pile.

[0051] The defect parameters obtained from the above detection were imported into finite element analysis software (such as ABAQUS or ANSYS) to establish a three-dimensional finite element model including the interaction between the pile, soil, and pile cap. The pile concrete was simulated using solid elements, the reinforcing steel was simulated using beam elements, and the soil was simulated using a Mohr-Coulomb constitutive model. The material parameters of the defect area were reduced according to the detection results: the elastic modulus of concrete in the crack area was reduced to 30% of the original value, the segregation area was reduced to 50%, and the fracture area was set as a non-strength element.

[0052] Step 320: Determine the critical depth at which each engineering pile can still provide effective embedment under the current state through finite element model inversion analysis.

[0053] By applying horizontal loads and bending moments in stages, the stress state under actual working conditions is simulated, and the bending moment distribution and horizontal displacement response of each pile are analyzed through inversion. The critical depth is defined as the depth location corresponding to when the bending moment of the pile reaches its peak and then decays to 20% of the peak value. The critical depths of each pile are obtained from the analysis as follows: Pile #1: Critical Depth H critical = 3.2m (measured from the top of the pile); Pile #2: Critical depth H critical = 3.0m; Pile #3: Critical Depth H critical = 3.8m; The remaining 5 piles: critical depth H critical = 2.2m (based on the empirical value of intact piles).

[0054] Based on the above critical depth, the overall remaining horizontal bearing capacity of all engineering piles is calculated to be 68% of the original design value, and the remaining flexural bearing capacity is 62% of the original design value. The assessment conclusion is that the overall bearing capacity of the pile foundation is seriously insufficient and reinforcement treatment is necessary.

[0055] Step 400: Reinforce the engineering piles based on the assessment results.

[0056] Step 410: Determine the bottom depth of the newly built and deepened foundation based on the critical depth.

[0057] Based on the critical depths of each pile obtained in step 320, the maximum value of 3.8m is taken as the design benchmark. The bottom depth D of the newly constructed and deepened pile cap is calculated using the following formula: D≥ H critical + Δ Among them, H criticalThe critical depth is 3.8m in this embodiment; Δ is the safety reserve thickness, which is 0.5m in this embodiment (determined according to the requirements of the "Code for Design of Strengthening Concrete Structures" GB 50367-2013, combined with the importance of the project). Therefore, D≥4.3m, and the final design uses D = 4.5m.

[0058] Step 420: Construct new pile foundations on the outside of the existing pile cap, with all new pile foundations arranged perpendicular to the central axis of the rotary kiln.

[0059] Based on the assessment results, six new bored piles are needed, each with a diameter of 800mm, a length of 25m, and a single pile bearing capacity characteristic value of 2500kN. The plan layout of the new pile foundations is as follows: three piles are arranged on each side along the length of the existing pile cap, and the line connecting the centers of all new pile foundations is perpendicular to the central axis of the rotary kiln. This arrangement ensures that the bending stiffness direction of the new pile foundation group is consistent with the direction of the main moment generated by the operation of the rotary kiln, thus providing the most effective resistance to the moment.

[0060] Step 430: Excavate the earth to the bottom depth to form the space for the new and deepened foundation, and combine the existing foundation and the new and deepened foundation through a synergistic reinforcement structure to form an integral composite foundation.

[0061] First, earthwork was excavated around the existing foundation to a depth of 4.5 meters to create space for pouring the new, deeper foundation. During the excavation process, segmented excavation and timely support measures were implemented to ensure the safety of the existing structure.

[0062] The newly constructed and deepened foundation has the following dimensions: length × width × height = 12m × 6m × 4.5m, and will be cast in place using C40 concrete. A triple-reinforcement method will be adopted for the interface treatment of the new and old concrete: First step: High-strength chemical anchors (25mm diameter, HRB400 grade, 500mm depth, 200mm×200mm spacing) are implanted on the side of the existing pile cap as the main shear keys; The second step involves pre-embedding a grouting network at the bonding surface. The network uses PVC pipes with a diameter of 20mm, and grouting holes are opened every 200mm on the pipe wall. After the new concrete is poured and reaches 70% of the design strength, epoxy resin grout is injected into the bonding surface through the grouting pipes. The grouting pressure is controlled at 0.2-0.4MPa. The third layer: A layer of carbon fiber composite fabric (300g / m²) is laid on the outer surface of the interface between the old and new concrete. 2 (Tensile strength ≥3400MPa), with a width covering 500mm on each side of the joint surface, providing additional shear and tensile strength.

[0063] After the new and deepened foundation cap is poured, it forms an integral composite foundation cap together with the existing foundation cap and the newly added pile foundation. After reinforcement, the horizontal bearing capacity and flexural bearing capacity of the entire foundation system are restored to more than 1.2 times the original design value.

[0064] Example 2 This embodiment is basically the same as Embodiment 1, except that the depth of the bottom surface of the newly built and deepened foundation is determined and the specific implementation method of the collaborative reinforcement structure is different.

[0065] In this embodiment, for a metallurgical rotary kiln foundation reinforcement project, the critical depth H was determined through testing. critical =5.2m. Considering the high importance level of this rotary kiln, the safety reserve thickness Δ is taken as 0.8m. Therefore, the bottom depth of the newly built and deepened foundation is D = 6.0m.

[0066] Regarding the synergistic reinforcement structure, this embodiment uses bolted steel plates instead of carbon fiber cloth as a third layer of reinforcement. Specifically, chemical bolts (M20×300mm, spaced 300mm×300mm) are pre-embedded on the outer surface of the interface between the old and new concrete. After the new concrete is poured, a 10mm thick Q345B steel plate is installed. Epoxy resin is injected between the steel plate and the interface, and the plate is secured with nuts. The steel plate covers a 600mm radius on each side of the interface.

[0067] After reinforcement, the rotary kiln underwent a vibration retest. The kiln pier amplitude decreased to within 2mm, meeting production requirements. A second retest after one year of operation showed stable vibration parameters, indicating that the reinforcement effect was durable and reliable.

[0068] Example 3 This embodiment provides a rotary kiln foundation pile foundation reinforcement system, which is applied to the diagnosis and reinforcement method of rotary kiln foundation pile foundation described in Embodiment 1 or Embodiment 2.

[0069] The reinforcement system includes: Integral composite foundation, including existing foundations and newly built, deepened foundations; Multiple new pile foundations were installed on the newly built and deepened pile cap.

[0070] Among them, the bottom depth D of the newly built and deepened foundation is based on the critical depth H. critical It is determined that D ≥ H critical +Δ, where Δ is the safety reserve thickness.

[0071] All new pile foundations are located within the newly built and deepened pile cap, and the arrangement direction of all new pile foundations is perpendicular to the central axis of the rotary kiln, so as to resist the main torque generated by the operation of the rotary kiln in the best way.

[0072] A synergistic reinforcement structure is provided at the interface between the existing foundation and the newly constructed, deepened foundation. The synergistic reinforcement structure includes: Chemical anchoring for implantation into existing foundations; Grouting pipe network pre-embedded in the joint surface; Carbon fiber composite fabric or bolted steel plate laid on the surface of the bonding surface.

[0073] This reinforcement system integrates the old and new structures into a unified whole that works together to bear the load through an integral composite foundation, fundamentally eliminating the source of vibration and ensuring the permanence and reliability of the reinforcement.

[0074] To enable those skilled in the art to better understand this invention, the relevant terms are explained as follows: Critical depth: refers to the depth at which a pile foundation, under its current state of damage, can still provide effective anchorage to the superstructure. Below this depth, the pile remains intact and can fully utilize its bearing capacity; above this depth, the pile is damaged, and its anchorage function is significantly weakened or fails.

[0075] Integral composite foundation: refers to an integral load-bearing structure formed by combining an existing foundation and a newly built, deepened foundation through synergistic reinforcement. The two structures can effectively transfer shear force and bending moment, jointly bearing the load from the superstructure.

[0076] Synergistic reinforcement structure: refers to a collective term for various reinforcement measures set at the interface between new and old concrete, including but not limited to chemical anchoring, grouting network, carbon fiber cloth, bolted steel plate, etc., which are designed to ensure that the new and old concrete work together and share the load.

[0077] To verify the technical effectiveness of this invention, the inventors conducted a comparative application in the foundation reinforcement project of rotary kiln No. 3 at a cement plant. The kiln pier was originally reinforced using traditional pile-filling methods, but severe vibrations recurred after two years of operation. After secondary reinforcement using the technical solution of this invention: Vibration amplitude: decreased from 8-12mm before reinforcement to 1.5-2.0mm after reinforcement, a reduction of over 80%; Bearing capacity recovery: Load tests have verified that the overall horizontal bearing capacity has recovered to 1.25 times the original design value; Long-term stability: After 12 months of continuous monitoring, the vibration parameters showed no significant changes, indicating that the reinforcement effect was durable; Economic benefits: It avoids production stoppage losses of approximately 8 million yuan per year and extends the service life of the foundation by more than 10 years.

[0078] The above verification results show that the technical solution of the present invention can effectively solve the technical problem of "repeated damage and repeated reinforcement" of rotary kiln foundation piles, and has significant technical effects and economic benefits.

[0079] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for diagnosing and reinforcing rotary kiln foundation piles, characterized in that, Includes the following steps: Obtain vibration data of the rotary kiln, and determine whether the vibration of the rotary kiln originates from damage to the basic structure based on the correlation between the vibration data and the rotation frequency of the rotary kiln. If so, all engineering piles supporting the rotary kiln are scanned to determine the defect type, location, and loss depth range of each engineering pile. Based on the defect type, location, and loss depth range of each engineering pile, the critical depth at which each engineering pile can still provide effective embedment under the current state is determined, and the overall remaining horizontal bearing capacity and flexural bearing capacity of all engineering piles are evaluated based on the critical depth to obtain the evaluation results. The engineering piles were reinforced based on the assessment results.

2. The method according to claim 1, characterized in that, The steps for determining whether the rotary kiln vibration originates from damage to the basic structure include: Perform spectral analysis on the vibration data to identify the dominant vibration frequency; Calculate the theoretical rotational frequency and its harmonics based on the actual operating speed of the rotary kiln; If the dominant vibration frequency matches the rotational frequency or its harmonics, then the vibration is determined to be unrelated to damage to the foundation structure. If the dominant vibration frequency is a fixed low-frequency peak that is independent of the rotational frequency and remains stable when the rotational speed changes, and is accompanied by a large displacement amplitude, then the vibration is determined to originate from damage to the foundation structure.

3. The method according to claim 1, characterized in that, The steps for scanning the engineering piles include: Ground-penetrating radar was used to conduct a general survey and scan of the soil under the pile cap, and the abnormal areas of the pile body were preliminarily delineated. Detection holes are drilled in abnormal areas, and ultrasonic cross-hole CT imaging technology is used to reconstruct the internal structure of the pile in three dimensions to determine the type, location and depth of defects.

4. The method according to claim 1, characterized in that, The step of determining the critical depth includes: A finite element model is established based on the defect type, location, and loss depth range; Through inversion analysis, the critical depth at which each engineering pile can still provide effective embedment under the current condition was determined.

5. The method according to claim 1, characterized in that, The steps for reinforcing the engineering piles include: Based on the critical depth, determine the bottom depth of the newly constructed and deepened foundation; New pile foundations will be constructed on the outside of the existing pile cap, and the arrangement direction of all new pile foundations will be perpendicular to the central axis of the rotary kiln. Excavate the earth to the bottom depth to create space for the new and deepened foundation. Combine the existing foundation with the new and deepened foundation through a synergistic reinforcement structure to form an integral composite foundation.

6. The method according to claim 5, characterized in that, The bottom depth of the newly constructed and deepened foundation meets the following formula: D≥H critical +D Where D is the bottom depth, H critical The critical depth is Δ, and the safety reserve thickness is Δ≥0.2m.

7. The method according to claim 5, characterized in that, The synergistic enhancement structure includes one or more of the following measures: High-strength chemical anchors are implanted as shear keys; Pre-embedded grouting pipeline network, used for pressure injection of epoxy resin grout at the interface; Carbon fiber composite fabric or bolted steel plate is laid on the interface surface.

8. The method according to claim 1, characterized in that, The vibration data includes vibration acceleration, frequency, and displacement amplitude, which are acquired by arranging vibration sensors on the rotary kiln bearing housing and kiln pier.

9. A rotary kiln foundation pile foundation reinforcement system, characterized in that, include: Integral composite foundation, including existing foundations and newly built, deepened foundations; Multiple new pile foundations were installed on the newly built and deepened pile caps; The bottom depth of the integral composite foundation is determined based on the method described in any one of claims 1-8.

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